In a bunch of Slavic languages pederast colloquially means homosexual, probably a holdover from the past.
So we have an old specific meaning that combines a 1) male 2) adult targeting a 3) male 4) child. This allows for a whole range of possibilities and thus possible disambiguties, if one or several of the four components were relaxed.
There are some parallels with the history of the word "homosexuality", because "homo" in Latin can mean both: "male human" or "human in general". The word often excluted female homosexuality, when it was limited to the performance of a particular sexual practice, namly anal penetration.